Hi all i have a 54 liter tank with only 1 betta and no decorations as of yet but will be getting them soon i would like to keep my betta in the same tank with the other fish but have a divider or mesh to seperate the two sides.

Is this a good idea for such a small tank? I would like some advise, Please help!

I would not do this. Most fish are better (=healthier and therefore "happier") in more space, the most we can give them. A betta will do fine, on its own, in a 5g planted tank. Or in the 14g with some live plants, if that is all you want. Most betta do not fare well with other fish, except perhaps some small catfish. Shrimp can work, though some report the Betta may eat them.

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.[unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]

The real issue I'm seeing here isn't the space (though that would give me pause) but the visuals. Although the divider will eliminate any physical bullying of other fish by the beta, it's been made clear that stressed fish aren't happy fish. With only a divider every other fish you put in that tank will be able to see the beta. The beta will likely still "stalk" the fish on the other side, flaring fins and creating stress.

The real issue I'm seeing here isn't the space (though that would give me pause) but the visuals. Although the divider will eliminate any physical bullying of other fish by the beta, it's been made clear that stressed fish aren't happy fish. With only a divider every other fish you put in that tank will be able to see the beta. The beta will likely still "stalk" the fish on the other side, flaring fins and creating stress.

Not a happy environment for anyone.

That is very true, and an aspect I overlooked. Thanks Natalie for mentinoing this, it is something we must all bear in mind. B.

The aquarist is one who must learn the ways of the biologist, the chemist, and the veterinarian.[unknown source]

Something we all need to remember: The fish you've acquired was quite happy not being owned by you, minding its own business. If you’re going to take it under your wing then you’re responsible for it. Every aspect of its life is under your control, from water quality and temperature to swimming space. [Nathan Hill in PFK]